The in vitro activity of ceftezol (demethylcefazolin) against dense populations of Escherichia coli.

The activity of ceftezol was examined by continuous turbidimetric monitoring of dense populations of Escherichia coli exposed to the drug. Although ceftezol was found to be very active against strains of E. coli, its activity was consistently less than that of the closely related antibiotics, cefazolin. This difference was also found when strains of E. coli were examined in a dynamic system which simulates some of the conditions in which bacteria and drug interact in the treatment of bacterial cystitis. Evidence is presented that the difference in activity between the two cephalosporins resides in a differential ability to induce certain morphological changes in E. coli and in a differential rate of destruction by escherichial beta-lactamases.